Tumors in fish caught in polluted waters: possible explanations.

The largest excess in tumor incidence due to pollution (616%) was observed in the fish species: Ictalurus nebulosis (the brown bullhead). Extensive analysis of waters on the Fox River in Illinois disclosed a heavy chemical and physical organic and inorganic materials far exceeding State and Federal minimal safety standards. Additional tests showed the presence of numerous human viral agents in the Fox River. Certain chemicals in the water appear to be potential carcinogens for fish. Two types of leukemia were found in 11% of the Esox lucius caught in the Fox River. It is hypothesized that these leukemias might also be of viral etiology. Experiments were conducted on Esox lucius caught in the Fox River. It is hypothesized that these leukemias might also be of viral etiology. Experiments were conducted on Esox lucius (Northern Pike). Interest centered around the possible viral origin of lymphosarcoma of the jaw in that species. Cell-free filtrates of this tumor were inoculated into a test group of fish from pollution-free waters. At the end of seven weeks, lymphosarcoma developed in 89% of the fish inoculated with cell-free homogenates. Control fish receiving inoculation of either Hank's balanced salt solution (HBSS) or normal tissues and kept in separate tanks at all times did not develop lymphosarcomas.